Stanford
researcher Mark Z. Jacobson developed a special computer model of air
pollution, weather and global climate that has atmospheric processes
that do not appear in other models. With this, he observed the
effects of soot from both fossil fuels like gasoline, coal and
diesel, and from solid biofuels like dung, wood and manure. According
to his findings, both types of soot combined together is the
"second-leading cause of global warming after carbon dioxide."

Climate
models previous to Jacobson's have misread the effects of soot in the
atmosphere, hence, it has been ignored when it comes to national and
international global warming policy legislation. Soot is now second
place in the global
warming contribution ranks, putting itself above methane.
Soot also "prematurely" claims the lives of more than 1.5
million people each year, and causes respiratory illnesses in
millions more worldwide.

While
decreasing carbon emissions is important and at the top of the list,
reducing soot emissions from fossil fuels and solid biofuels could
slow the progression of global warming almost instantly. Jacobson
came to this conclusion because soot only lingers in the atmosphere
for a few weeks, and then it is washed out. Contrarily, carbon
emissions stay in the atmosphere up to a century, which is a large
gap of time before visible results of emission cuts are available.

"Controlling
soot may be the only method of significantly slowing Arctic warming
within the next two decades," said Jacobson. "We have to
start taking
its effects into account in planning our mitigation efforts
and the sooner we start making changes, the better."

During
the last century, the Arctic's net warming has been at 2.5 degrees
Celsius, and will only get warmer if no action is taken. By reducing
soot emissions, warming above the Arctic Circle will decrease over
the next 15 years by as much as 1.7 degrees Celsius.

While
these two types of soots combined are largely contributing to global
warming, the soots individually are just as dangerous. Soot caused by
the burning of fossil fuels is more of a contributor to global
warming while soot caused by the burning of solid biofuels is more
dangerous to humans. Solid biofuel soot causes eight times more
deaths as fossil fuel soot.

The
difference between the two types of soot is black carbon, which is
found in the fossil fuel soot and has a significant effect on warming
over the Arctic. Black carbon absorbs solar radiation, converts
sunlight to heat and radiates it back to its
surroundings (air). It is able to absorb light reflecting away
from the Earth's surface as well. This is particularly threatening to
the Arctic because the black carbon is in the air over ice or snow,
sunlight hits the black carbon both while coming toward Earth and
when it reflects off the ice and back into space.

"There
is big concern that if the
Arctic melts, it will be a tipping point for the Earth's
climate because the reflective sea ice will be replaced by a much
darker heat-absorbing ocean below," said Jacobson. "Once
the sea ice is gone, it is really hard to regenerate because there is
not an efficient mechanism to cool the ocean down in the short term."

Researchers
have found that the best way to reduce soot emissions is to attach
particle traps, which filter soot particles from exhaust, to vehicles
like buses and diesel trucks. This is a cheap, effective and fast way
of taking care of the issue. Another way to eliminate soot would be
the use of electric vehicles, but automakers are just now releasing
these cars onto the market, and it will take some time to push
gasoline-powered vehicles completely out of the picture.

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